It is mainly rural and is situated largely in the basin of the River Erne. It is dominated by two connected lakes: Upper and Lower Lough Erne, and, including water, spans an area of 1,851 km² (715 sq; mi).[6] It is approximately 120 km (75 mi) from Belfast and 160 km (99 mi) from Dublin.

Fermanagh accounts for 13.2% of land mass of Northern Ireland and 30% of Fermanagh is covered with lakes and waterways.

Fermanagh was a stronghold of the Maguire clan and Donn Carrach Maguire (died 1302) was the first of the chiefs of the Maguire dynasty. However on the confiscation of lands relating to Hugh Maguire, Fermanagh was divided in similar manner to the other five escheated counties among Scottish and English undertakers and native Irish. The baronies of Knockninny and Magheraboy were allotted to Scottish undertakers, those of Clankelly, Magherastephana and Lurg to English undertakers and those of Clanawley, Coole, and Tyrkennedy, to servitors and natives. The chief families to benefit under the new settlement were the families of Cole, Blennerhasset, Butler, Hume, and Dunbar.

Fermanagh was made into a county by statute of Elizabeth I, but it was not until the time of the Plantation of Ulster that it was finally brought under civil government.

Agriculture and tourism are two of the most important industries in Fermanagh. The main types of farming in the area are beef, dairy, sheep, pigs and some poultry. Most of the agricultural land is used as grassland for grazing and silage or hay rather than for other crops.